1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof.
2. Description of the Related Art
In recent years, development of a thin film transistor (TFT) which can be formed over a flexible substrate such as a plastic substrate or paper has been conducted actively to realize a sheet display, a sheet computer, and the like.
A TFT and an electronic circuit using the TFT are manufactured in such a way that various thin films such as a semiconductor film, an insulating film, and a conductive film are stacked over a substrate, and a predetermined pattern is formed by a photolithography technique, as appropriate.
The photolithography technique is a technique to transfer a pattern of a circuit or the like formed of a material that does not transmit light, which is formed over a transparent flat plate, a so-called photomask, to a targeted substrate by using light. The photolithography technique is widely used in manufacturing steps of a semiconductor integrated circuit or the like.
A conventional manufacturing process using a photolithography technique requires multiple steps such as exposure, developing, baking, and peeling only for treating a resist mask formed using a photosensitive organic resin material that is referred to as photoresist. Therefore, as the number of photolithography steps is increased, the production cost is inevitably increased. In order to improve such a problem, a TFT has been attempted to be manufactured by decreasing the number of photolithography steps (e.g., refer to Reference 1: Japanese Published Patent Application No. 2000-133636).